The Weasley twins

Appearance:
Like all Weasleys, they have bright red hair, blue eyes, and barely noticeable freckles on their cheeks and nose.
Twins are very similar to each other, and even their parents often confuse them.

Character:
Fred is more active, proactive, and daring. He often instigates pranks. Sometimes his jokes can be quite cruel.
George is more reserved and tactful. He often acts as the twins' "face," smoothing over rough edges and helping Fred think through the details.

The brothers balance each other out: Fred brings energy and ideas, and George sees them through to completion. They love pranks, are talented Quidditch players (they're Beaters on the Gryffindor team), and eventually open a joke shop, Weasleys' Wizard Wheezes.

The Weasley family
Parents:
Arthur Weasley is the father, a wizard who works at the Ministry of Magic and is interested in Muggle inventions. In the books, he is described as thin, receding, and bespectacled; in the films, his appearance is different.
Molly Weasley is a mother, caring and strict, always supporting her children.

Children:
Bill, Charlie, Percy are the older brothers.
Ron is the youngest son and best friend of Harry Potter.
Ginny is the only daughter in several generations.

Family characteristics:
The Weasleys are a pureblood family, but are considered "blood traitors" by blood purists because they are loyal to Muggles and Muggle-borns.
The family is not rich, but an atmosphere of love and mutual assistance reigns within it.
All the children studied in the Gryffindor house.